Vibration generation systems, or "shakers," have a variety of uses, including:
(a) calibration of acceleration, velocity and displacement transducers;
(b) vibration testing;
(c) structural acoustics testing;
(d) resonance searching;
(e) study of the dynamic and acoustic properties of structures and structural models;
(f) mechanical impedance and mobility measurements;
(g) structural response testing;
(h) educational demonstration of vibration and acoustic phenomenon;
(i) fatigue testing of specimens;
(j) environmental testing of objects and structures; and
(k) active sound and vibration control.
In some of the above-noted uses, there is a need for a compact, lightweight, high-force vibration source that can be used in confined spaces where conventional systems (such as mechanical, hydraulic, pneumatic or electromagnetic systems) would not fit. Other uses require a shaker with low power consumption to permit battery operation, for example for portable applications. Quiet operation may be required for other applications, such as in acoustics research. Still other applications may require a shaker with minimal heat dissipation. Moreover, there is always a need for reliable operation.
Some applications require a shaker with all of the above-noted characteristics, i.e. a compact, lightweight, portable, quiet, high-force shaker with low heat dissipation. For example, without limitation, one need for such a source is in the study of tissue response in mammals to the mechanical vibrations generated by artificial hearts and ventricular-assist devices. These studies require a shaker that can be implanted in research animals (calves) for reproducing complicated acceleration vibration patterns measured in an artificial heart, with peak levels up to 100 times gravity (981 meter per second squared), and various other requirements, including that it be small in volume, or "compact" enough to be implanted in the thoracic cavity, that it be lightweight so that it does not mass load or compress surrounding tissue, that it not require high voltages or currents, that it not heat up significantly during the operation, and that it be portable and capable of operating with batteries as the power supply.
As described more fully below, the magnetostrictive vibration generation system of the present invention attains a unique combination of characteristics which can individually or together meet a wide variety of unique requirements for shaker systems.